This section contains a basic profile of lighting use in residential households. It includes brief discussions about the characteristics and location of lights used in residential households, as well as descriptions of the amount of electricity used for lighting and variations in households' consumption of electricity for lighting.

Dominance of Incandescent Lights

The majority of light bulbs in residential households are incandescent. According to the RECS Survey, 453 million lights out of a total of 523 million used one or more hours per day are incandescent (87 percent).[8] The Lighting Supplement also estimates that 87 percent of residential lights used 15 minutes or more per day are incandescent.

Fluorescent Lights of All Types

Thirteen percent, or 69.5 million lights used one or more hours per day are fluorescent. Fluorescent lights tend to be used more hours per day than incandescent lights. Twenty-one percent of the lights used more than 12 hours per day are fluorescent lights (see Table 2.1).[9]

Table 2.1 Fluorescent Lights as a Percent of Total Lights

Compact Fluorescent Lights

According to the RECS Survey, compact fluorescent lights are used in 8.9 percent of residential households, although 49 percent of the homes reported knowing about them. [10] The percentage of households using compact fluorescent lights varies slightly by Census region, with households in the Northeast being somewhat more likely to use them, presumably due to higher electricity prices. The Lighting Supplement data show that less than one percent of all lights used 15 minutes or more per day are compact fluorescent.

Halogen Lights

A halogen light is a type of incandescent light that is slightly more efficient than the common incandescent light. A 100-watt common incandescent produces 17.5 lumens per watt compared with a 100-watt halogen, which produces 18.8 lumens per watt. These differences are much smaller than the comparison with the compact fluorescent, but the typical cost of a halogen light is 4 dollars versus 20-22 dollars for a compact fluorescent. Halogen lights are more widely known than the compact fluorescent (66 percent of households have heard of them), but they are used in only 12 percent of homes. Again, the RECS Survey shows this varies by Census Region, with households in the Northeast and West being somewhat more likely to use halogen lights.

Location of Lights

Rooms

Incandescent lights predominate in all rooms in the household, both in number and in hours used (Figure 2.1). In all rooms, except for the kitchen and "other" (which includes laundry rooms), incandescent lights account for at least 90 percent of the hours used. Although the kitchen and "other rooms" contain the most fluorescent lights, fluorescent lights in these rooms still account for only 30 to 33 percent of the hours used.

Rooms that contain the most lights do not necessarily consume the most electricity for lighting. For example, bedrooms have the most lights, followed by the kitchen and the living room. However, the lights in the kitchen are used the most hours, followed by the living room and bedrooms (Figure ES5).

For lights used at least 15 minutes per day, the average use per light in kitchens is about 3.8 hours, followed by living rooms (3.4 hours per light), and family rooms (3.3 hours per light). Rooms where lights are used less intensively are bedrooms (1.6 hours per light) and bathrooms (1.8 hours per light).

Outdoor Lights

About two-thirds of U.S. homes use outdoor lighting. The percentage is much lower for apartments in buildings containing 5 or more units. In these structures, only 28 percent of the households reported using an outdoor light. [11] The percentage using outdoor lights in other types of structures is 76 percent for single-family homes, 69 percent for mobile homes, and 59 percent for small apartment buildings (2 to 4 units).

In approximately half of the households that use outdoor lights, the wattage of all outdoor lights combined for each household is below 150 watts. We may assume it is over 150 watts for the other half. [12] Lights are turned on for the evening in 41 percent of the homes, while other homes using outdoor lights leave them turned on all night or have them controlled in some way. Only three percent of homes use a high-intensity discharge light outdoors (see the Glossary for definitions of different types of lights).

Lighting Usage and Costs

Usage

In 1993, the average household consumed 940.5 kWh of electricity for lighting. Electricity consumption for lighting increases with increasing income, number of household members, and number of rooms in the housing unit (see Tables 4.9, 4.10, and 4.11 of the Detailed Tables). Consumption also varies with Census region. Households in the South and Midwest consume the most electricity for lighting (Figure 2.2). Perhaps this is because electricity costs less in those Census regions.

An alternative way of displaying electricity consumption for lighting is to show the percent of households in consumption categories. For example, Figure 2.3 shows a distribution of households, for each household type, by the amount of electricity for lighting, in 250 kWh increments. The largest number of apartments (32.9 percent) consume between 250 and 499 kWh. The largest number of mobile homes (24.0 percent) consume between 500 and 749 kWh. Among single-family homes, the consumption is higher, with 17.4 percent using between 750 and 999 kWh.

Costs

The RECS survey shows that the average annual cost of electricity for lighting is approximately 83 dollars per household (1993 dollars), which is about 10 percent of the average expenditures on electricity in 1993 ($840). The 25th and 75th percentiles show that 25 percent of the households paid less than 43 dollars and 25 percent paid more than 109 dollars. One-half paid between 43 dollars and 109 dollars. Although households in the South and Midwest consumed more electricity for lighting, households in the Northeast paid the most for electricity for lighting because they had the highest average electricity prices (Figure 2.4).

Variation in Lighting Consumption Among Households

The annual electricity consumption for lighting in 1993 was 940 kWh per household--9 percent of the total consumption. This figure includes both indoor and outdoor lights. Figure 2.5 shows the cumulative percent of households by annual electricity consumption for lighting. The median consumption for all households is 818 kWh. Households in single-family homes use the most electricity for lighting, while households in apartment buildings use the least (median of 953 and 484 kWh, respectively).

Just as total energy use varies considerably from one household to another, so does the percentage of electricity used for lighting. This percentage varies because of the different uses that are made of electricity. Some households use electricity for some heavy work--heating the home, water heating, and air-conditioning, so their bills will be large and the lighting component a small part of the bill. Other households not using electricity for these heavy loads will show a higher percentage of their electricity used for lighting.

The variation in the percentage of electricity used for lighting depends on the cost of electricity, what it is used for, and the climate where the household is located. Unlike space heating and water heating, where nonelectric energy sources are chosen when the cost of electricity gets too high, alternative sources for lighting are not much used today. Consequently, in areas where the cost of electricity is high, one sees a small decrease in the amount of electricity used for lighting (Table 2.2), although these smaller amounts represent a larger share of the total electricity bill.

Table 2.2 Regression Allocation Estimates of Kilowatthours Used for
Lighting by the Cost of Electricity, 1993

Cost of Electricity (cents per kWh)	Annual kWh for Lighting
	Single-Family Home	Apartment	Mobile Home
0 to 7.49	1,134	636	875
7.5 to 12.49	1,051	584	869
12.5 or More	942	512	Q

Q=Data withheld because fewer than 10 households were sampled.
Source: Energy Information Administration, Office of Energy Markets and End Use, Forms EIA-457A, B, E, and H of the 1993 Residential Energy Consumption Survey and EIA-861 of the 1993 Annual Electric Utility Report.

Lighting Consumption Compared to Other End Uses

Lighting accounted for 9.4 percent of all electricity consumption in U.S. households in 1993, less than air conditioning, water heating, space heating, or refrigeration (Figure ES4). [13] Residential lighting thus represents three percent of total U.S. sales of electricity to all sectors. [14] Because the end-use estimates do not distinguish between indoor and outdoor lighting, this estimate of lighting consumption includes both.

Virtually 100 percent of households use electricity for lighting, while less than 70 percent use it for air conditioning and less than 40 percent use it for space heating and water heating. However, because space conditioning and water heating are more intensive users of electricity than lighting, they account for a greater amount of the total electricity consumption in the residential sector. In 1993, air conditioning consumed 13.9 percent, water heating 10.2 percent and space heating 12.3 percent. Lighting consumed 9.4 percent.

Estimating the Number of Indoor Lights

The number of indoor lights used 1 hour or more per day can be predicted with some accuracy from knowing one fact about people (the number of persons in the household) and one fact about the housing structure (the number of rooms). The number of indoor lights can be predicted from the following equation:

For this calculation, rooms are defined as kitchens, dining rooms, living rooms, family rooms, and bedrooms. Rooms do not include bathrooms, basements, or utility rooms. For example, one person living in a four-room housing unit would be expected to use about four lights for one hour or more per day. Other factors, such as the age of the occupants, would be expected to affect this estimate for any particular household.

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